Method and apparatus for altering the effective mode index of an optical waveguide
An effective index modifier that modifies light propagation in a waveguide. The device is formed on a wafer, such as a Silicon-On-Insulator (SOI) wafer that includes an insulator layer and an upper silicon layer. A waveguide is formed at least in part in the upper silicon layer of the SOI wafer. The waveguide guides an optical signal by total internal reflection. At least one micro-mechanical system (MEMS) having at least one movable component is disposed a positive distance away from the waveguide. Application of voltage to the MEMS results in a variation of the distance between the moveable component and the waveguide, which in turn alters the effective index of the waveguide in a location proximate the moveable object, thereby resulting in modification of light propagation in the waveguide.
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This application claims priority to U.S. Provisional Patent Application Ser. No. 60/352,817 entitled “Method And Apparatus For Altering Effective Mode Index Of Waveguide,” filed Jan. 30, 2002, incorporated herein in its entirety by reference.
FIELD OF THE INVENTIONThis invention relates to optical waveguide devices, and more particularly to semiconductor optical waveguide devices.
BACKGROUND OF THE INVENTIONIn the integrated circuit industry, there is a continuing effort to increase device speed and increase device densities. In addition, manufacturers continue to search for technologies that can be used to implement optical functions at low cost.
Prior U.S. patent application Ser. No. 10/146,351, filed May 15, 2002, Ser. No. 09/991,542, filed Nov. 10, 2001, and Ser. No. 09/859,693, filed May 17, 2001, each of which is owned by the assignee of the present application and herein incorporated by reference, describe various optical components that can be formed at low cost on semiconductor wafers using standard CMOS processing techniques. In these prior applications, an electrode was used to project a region of altered propagation constant into a semiconductor waveguide in order to achieve a given optical function. The present application describes still further optical systems that can be formed on semiconductor wafers.
SUMMARY OF THE INVENTIONThe present invention is directed to an effective index modifier that modifies light propagation in a waveguide. The device is formed on a wafer, such as a Silicon-On-insulator (SOI) wafer that includes an insulator layer and an upper silicon layer. A waveguide is formed at least in part in the upper silicon layer of the SOI wafer. The waveguide guides an optical signal by total internal reflection. At least one micro-electro-mechanical system (MEMS) having at least one movable component is disposed a positive distance away from the waveguide. Application of voltage to the MEMS results in a variation of the distance between the moveable component and the waveguide, which in turn alters the effective mode index of the waveguide in a location proximate to the moveable object by virtue of the evanescent optical field, thereby resulting in modification of light propagation in the waveguide.
In one embodiment, the moveable component is moveable along a first axis that is normal to the plane of the wafer. The moveable component can also be made to be moveable in a plane that is parallel to the wafer plane and that is perpendicular to the first axis. In a still further embodiment, the moveable component is made to be moveable in a plane that is parallel to the wafer plane, and can be made to rotate about the first axis that is perpendicular to the wafer plane.
The shape of the moveable component can be varied in order to implement different optical functions. For example, the moveable component can alternatively be formed in the shape of optical lenses, prisms, Echelle lenses or gratings, etc., in order to implement corresponding optical functions using the present invention.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.
Throughout the figures, unless otherwise stated, the same reference numerals and characters denote like features, elements, components, or portions of the illustrated embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTReferring now to
In the present invention, upper silicon layer 12 acts as a waveguide that limits the locations in which light can diffract within wafer 10. The waveguide guides light by total internal reflection. Making the upper silicon layer 12 thin, acts to localize the light to a relatively narrow waveguide. Various systems for coupling optical signals into and out of waveguide 12 are shown in U.S. patent application Ser. No. 10/146,351, filed May 15, 2002, which is assigned to the assignee of the present invention, and incorporated herein in its entirety by reference.
Effective mode index modification system 100 also includes a movable object 20, which in the preferred embodiment, is formed as a micro-electro-mechanical systems (MEMS). MEMS device movable object 20 comprises a material (for example, polysilicon, silicon nitride, doped glass or a polymer) and optionally includes a thin film coating 22. As discussed in the co-pending application Ser. No. 010/146,351, the evanescent electrical field penetrating outside of a silicon waveguide can be perturbed by bringing a component near the waveguide. In accordance with the present invention, the same principle is used to manipulate the optical mode in the waveguide. When a MEMS movable object is brought in the vicinity of the waveguide surface, the optical mode propagating in the waveguide experiences a perturbation as a function of the distance between the movable object and the waveguide, the shape of the movable object, and the respective refractive indexes of both elements. Thus, the optical mode behavior in the waveguide can be modified using this MEMS movable object to achieve various functionalities. Applications of this effect are known in the art, for example, the waveguide investigation performed using a near-field scanning optical microscope (NSOM) is based upon the principle of probing the evanescent field. Additionally, several chemical and biological sensors are based upon evanescent field interaction. In the embodiment shown in
Referring now to
Referring now to
In further embodiments, movable object 20 may be given a specific shape, in order for system 100 to perform a given optical function. For example, in
Although in
In addition to the lens-shaped movable object 20 shown in
System 100, including SOI wafer 10 and MEMS device 20, can be fabricated using well known CMOS processing techniques. Accordingly, using the present invention, multiple MEMS objects 20 may be positioned at different locations proximate a single SOI wafer 10, in order to form more complicated optical devices. For example, an optical switch formed in this manner is shown in
While the principles of the invention have been described above in connection with the specific apparatus and associated methods set forth above, it is to be clearly understood that the above description is made only by way of example and not as a limitation on the scope of the invention as defined in the appended claims.
Claims
1. An effective mode index modifier that modifies light propagation in a waveguide, comprising:
- a Silicon-On-Insulator (SOI) wafer that includes an insulator layer and an upper silicon layer;
- a waveguide formed at least in part in the upper silicon layer of the SOI wafer, wherein the waveguide guides an optical signal by total internal reflection;
- at least one micro-electro-mechanical system (MEMS) having at least one movable component disposed a positive distance away from the waveguide;
- wherein application of voltage to the MEMS results in a variation of the distance between the at least one movable component and the waveguide, which in turn alters the effective mode index of the waveguide in a location proximate to the at least one movable component moveable object, thereby resulting in modification of light propagation in the waveguide.
2. The effective mode index modifier of claim 1, wherein the at least one movable component is movable along a first axis that is normal to a plane of the wafer.
3. The effective mode index modifier of claim 1, wherein the at least one movable component is movable throughout a second plane that is parallel to the plane of the wafer and perpendicular to the first axis.
4. The effective mode index modifier of claim 3, wherein the at least one movable component is able to rotate about the first axis.
5. The effective mode index modifier of claim 3, wherein the at least one movable component is able to rotate about a third axis that is perpendicular to the plane of the wafer.
6. The effective mode index modifier of claim 1, wherein the at least one movable component has a shape that corresponds to a shape of a lens.
7. The effective mode index modifier of claim 6, wherein the at least one movable component has a shape that corresponds to a prism.
8. The effective mode index modifier of claim 7, wherein the at least one movable component is movable along a first axis that intersects said upper silicon layer.
9. An effective mode index modifier that modifies light propagation in a waveguide, comprising:
- a wafer that includes an insulator layer and an upper silicon layer;
- a waveguide formed at least in part in the upper silicon layer of the wafer, wherein the waveguide guides an optical signal by total internal reflection;
- at least one micro-electro-mechanical system (MEMS) having at least one movable component, the at least one movable component disposed a positive distance away from the waveguide;
- wherein application of voltage to the MEMS results in a variation of the distance between the at least one movable component and the waveguide, which in turn alters the effective mode index of the waveguide in a location proximate to the at least one movable component, thereby resulting in modification of light propagation in the waveguide.
10. A method for modifying light propagation in a waveguide, comprising the steps of:
- providing a Silicon-On-Insulator (SOI) wafer that includes an insulator layer and upper silicon layer, and a waveguide formed at least in part in the upper silicon layer of the SOI wafer, wherein the waveguide guides an optical signal by total internal reflection, and at least one micro-electra-mechanical system (MEMS) having at least one movable component comprising a material having a refractive index less than the refractive index of silicon, the at least one movable component disposed a positive distance away from the waveguide; and
- applying a voltage to the MEMS which results in a variation of the distance between the at least one movable component and the waveguide, which in turn alters an effective mode index of the waveguide in a location proximate to the at least one movable component, thereby resulting in modification of light propagation in the waveguide.
11. A method for modifying light propagation in a waveguide, comprising the steps of:
- providing a wafer that includes an insulator layer and upper silicon layer, and a waveguide formed at least in part in the upper silicon layer of the SOI wafer, wherein the waveguide guides an optical signal by total internal reflection, and at least one micro-electra-mechanical system (MEMS) having at least one movable component disposed a positive distance away from the waveguide; and
- applying a voltage to the MEMS which results in a variation of the distance between the at least one movable component and the waveguide, which in turn alters an effective mode index of the waveguide in a location proximate to the at least one movable component, thereby resulting in modification of light propagation in the waveguide.
12. The effective mode index modifier of claim 6, wherein the at least one movable component has a shape that corresponds to a grating.
6389189 | May 14, 2002 | Edwards et al. |
20030003735 | January 2, 2003 | Deliwala |
20030003736 | January 2, 2003 | Delwala |
20030003737 | January 2, 2003 | Delwala |
Type: Grant
Filed: Jan 29, 2003
Date of Patent: Apr 12, 2005
Patent Publication Number: 20030165288
Assignee: SiOptical, Inc. (Allentown, PA)
Inventor: Shrenik Deliwala (Orefield, PA)
Primary Examiner: Akm Enayet Ullah
Assistant Examiner: Kevin S. Wood
Application Number: 10/354,155